Helicopter-borne Electromagnetics (HEM) German North Sea coast - Data (WMS)

This dataset has been compiled within the BGR project "D-AERO-Auswertung" based on several survey area located along the German North Sea coast. The BGR helicopter (Sikorsky S-76B) is used for airborne geophysical surveying of the Earth’s subsurface. The standard equipment comprises the methods electromagnetics, magnetics and radiometrics. The active multi-frequency, helicopter-borne electromagnetic (HEM) system, which consists of circular (diameter about 0.5 m) transmitter and receiver coils (horizontal separation about 8 m) operating at five and since 2007 at six system frequencies, is housed by a flying tube (bird) about 40 m beneath the helicopter. The HEM system used before 2002 consisted of rectangular coils (horizontal separation slightly less than 7 m) and five system frequencies (0.4 - 190 kHz). The ratio of received and transmitted signal yields to the electrical conductivity down to 50/150 m depth in case of conductive/resistive subsurface. The results are displayed as apparent resistivity (= half-space resistivity) and centroid depth maps at each of the six system frequencies ranging from 0.4 to 130 kHz.本数据集依托德国北海岸沿线的多个测量区域，由BGR项目"D-AERO-Auswertung"编制完成。本次探测使用BGR所属的西科斯基S-76B直升机，开展地球地下的航空地球物理勘探工作。标准探测设备涵盖电磁法、磁法与放射性测量法。该有源多频直升机载电磁系统（helicopter-borne electromagnetic, HEM）由直径约0.5米的圆形发射线圈与接收线圈构成，线圈水平间距约8米，最初仅支持5个系统工作频率，自2007年起扩展至6个；该系统搭载于直升机下方约40米处的飞行吊舱（业内俗称“鸟舱”）。2002年之前使用的HEM系统则采用矩形线圈，线圈水平间距略小于7米，支持5个系统工作频率（0.4~190 kHz）。针对导电或高阻地下介质，接收信号与发射信号的比值可反演得到其在50米（导电介质）/150米（高阻介质）深度范围内的电导率。最终结果将以视电阻率（即半空间电阻率）与质心深度图的形式呈现，覆盖0.4~130 kHz的6个系统工作频率中的每一个。